Virtualbox's enhancements package (VBoxGuestAdditions) must be installed
1. Open the Linux system, select Device -> Install Enhancement Enhancement
2. Wait for its automatic installation. When press return to close this window... appears, you can click Enter and restart the system;
3. Device -> Shared Folder, click Add New Folder
4. Create a folder on the physical machine with the name share
5. Create a share folder (mkdir /mnt/share) under the virtual machine /mnt, and execute in the terminal: mount -t vboxsf weshare /mnt/weshare/